Retinol or vitamin A alcohol is useful in the reduction of fine lines, wrinkles, and mottled hyperpigmentation in skin. Hydroxy acids, and particularly alpha-hydroxy acids, are useful in increasing the clarity of the skin surface, increasing cellular turnover, and increasing skin radiance and smoothness. Ascorbic acid has skin permeation and collagen synthesis activity.
Retinol is physically unstable and rapidly degrades when stored at a pH below about 5. Acids such as hydroxy acids, and particularly alpha-hydroxy acids and ascorbic acid, on the other hand, are not active in increasing skin cell turnover, exfoliation, skin permeation, and/or collagen synthesis at pHs above about 5.
Consequently, retinol and hydroxy acids and/or ascorbic acid have generally been packaged separately. Retinol typically is packaged in a vehicle at a pH above about 5, while alpha-hydroxy acids and ascorbic acid are packaged at a pH of about 4 or below. Therefore, one must apply two separate products in order to achieve the benefit of both of these ingredients.
The present inventors have discovered a single composition which include both of these ingredients, in which both of these ingredients are stable, and in which both of these ingredients are active upon application to the skin.